Granted, from the Senates own site at Senate.Gov, they admit there is no actual rule in place.

Senate Legislative ProcessThe practice of "holds" (requests by senators to party leaders to delay floor consideration of legislation or nominations), which is nowhere recognized in Senate rules or precedents and about which little is known with respect to its origins, has become a prominent feature of today's Senate

But it has been used often to stop a nomination. Will Republicans go nuclear with this procedural tool to stop the government from governing? Stay tuned for next week, next month, next year.

In almost every election, Republicans nominate what they see as the sensible moderate in sheep's clothing. Romney won the "electable" meme and became the nominee against the teaparty clamoring for a "Real Conservative." (NOTE - a Teaparty "Real Conservative" is the person who sounds sane to the crazies.) McCain won the "electable" meme and the nomination in 2008. Bush won the "electable" meme in 2000, and the White House, with that "Compassionate Conservative" lie while running against Bill Clinton's zipper, with the help of criminal acts and the Supreme Court.

As long as there are enough Republicans who want someone they think is electable by the independent center right voters, he will win the "electable meme." If an open crazy like Cruz wins the nomination, the Republican party will have completed its Wiginization and will be gone by 2020, replaced by a party that keeps its screaming crazies in a box.

This is why Christie is the most dangerous Republican in the current race. He is capable of looking normal to the independent, non-aligned voters in the center, many of whom are Republicans who were left without a party by the shifting definition of "Conservative" and the drive for ideological purity.